Bus duct



July 6, 193.7. H. .1.11.. FRANK original. Filled Feb. 15, 4 sheets-sheet1 A ZZ w LLl 4 Sheets-Sheet 2 H. J. LVFRANK BUS DUCT Original Filed Feb.l5. 1932 f mf mg f IW" ..llllnllll l/nul u .Fi NIIV July 6, 1937.

July 6, 1937. H. J. l.. FRANK Re. 20,436 y BUS DUCT Original Filed Feb.15, 1952 4 Sheets-Sheet 3 Il Il IIQIII."

Flam

Re. v20,436

July 6, 1937. H. J. 1:.. FRANK Bus DUCT Qrignal Filed Feb. 15, 1932 4Sheets-Sheet 4 INVEN'TOR ATTORNEY I. Reissued July 6, 1937' Harrison J.L. Frank,

Bulldog Electric Products Company,

Detroit, Mich., assignor to Detroit,

Mich., a corporation of West Virginia Original No. 2,043,796,

No. 592,912, February dated June 9. 1936, Serial 15, 1932. Applicationfor reissue June 20, 1936, Serial No. 86,436

31 Claims.

This invention relates to current distributing, systems of the typeshown and described andl claimed in my prior applications, Serial Nos.424,423, January 29, 1930, and 454,102, May 20, .5 1930, for whichapplications, this application is to be considered an amalgamatedcontinuation in part.

AnA object of the invention is a bus duct system of electricaldistribution which is intended to replace, in industry, older and lessemcien systems of electrical distribution.

'I'he embodiments of the invention disclosed hereinafter, include aplurality of -bus duct sections of unit or standard manufacturinglengths,- joined together to form a continuous, enclosed, distributionsystem, leading from the point of power input,- through factory walls,partitions, etc. up and down floors,.etc. to the points of power outlet,namely, electrical consuming de'- vices. In the enclosure part of thebus duct sections and insulated therefrom, are` relatively insulated-bus bars, Yfrom which power may be drawn at desired points throughsuitable outlets into which may be inserted or plugged, power take-offdevices, such as plugs.

Systems answering the general description given above include specicdetails which form` major parts of the inventions of this case. Amongthe details are (a) Novel forms of .power outlets.

from each other and from the duct.

(c) Novel methods of creating new power outlets a'nd of eliminating oldones. (d) Novel forms of parts not specifically included in theforegoing. l v

' Prior systems of distribution are not as satisfactory as the systemdisclosed hereinafter, for the following reasons:

(a) The novel system for outlet variation, etc. than older systems. glueto the hinged cover on the duct, and also due to the fact that theduct-is composed of short sections, joined as desired;

(b) The novel system is safer than, older systems, since the bus barsare completely insulated,

rigidied and'spaced, in the grounded du'ct, and

/since the original bus bar insulation is never broken, but is merelyshifted, asdesired, and may be replaced, as desired, without alterationin its insulating characteristics. It. will be observed that thisfeature is not true of insulated cable `systems, where the originalinsulation, when once removed, can not be restored, and must be re- 55placed by a taped joint, whichis, not as depend- (b) Novel means ofinsulating the bus barsv place.

is :more readily accessible a bus bar.

able, nor as readilyaccessible original woven insulation;

(c) The novel system is more flexible than oldr systems, due to the easewith which outlets are created or eliminated, due to the ease with 5which runs are added to a pre-existing system, due to theinterchangeability of parts, due to the facility with which plugs of onecapacity may be substituted for another, etc., without disturbing thebus duct itself.

' (d) The novel system is more easilyand eco-1 nomically installed,maintained, and altered, than older systems, due to the specific detailsof construction.

(e) 'I'he novel system lends itself more readily l5 than oldersystems tomass or factory production, for the parts thereof-are all standardized,to be assembled and installed as required.

(f) The vnovel system, as contrasted with older systems, dispenses withdistribution panels, loose 20 Wires, etc.

(g) The novel system is built up of a plurality of individual sections,each of which, before it is` assembled or mounted, is equipped andincludes a duct enclosure and the necessary bus 5 bars, insulation, etc.

Still further objects and advantages will readily occur tothose skilledin the art upon reference to the following description and theaccompanying drawings in which Fig. 1 is an elevation view of a sectionof the duct, with a current collecting plug shown in for testing as theF1g.'2 is a'section through the duct.

Fig. 3 is a bottom plan view of a power outlet. 35

Fig. 4 is a longitudinal 'section thereof, as if on' line l-l of Fig. 3.

Fig. 5 is a transverse section thereof, as if on the line 5-5 of Fig. 4.

Fig. 6 is a similar view but shown in connec- 40 tion with one form ofplug. l

Fig. '1, is a similar view of a slight modification, shown in connectionwith a second form of plug..

Fig. 8 is a perspective view of the power outlet.

Fig. 9 shows a length of bus bar, with outlet 45 'spacesI at certainpoints. f

Fig. 10 shows the same length vof bus bar, but' with the outlet spacesat different points. v Fig. l`1 is a longitudinal plan cross sectionview of a length of bus bar.-

Fig..l2 shows means for joining adjacent ends of bus bar sections. A

Fig. l3shows plug locking means on a duct.

Fig. 14 shows a modied\form of insulation for Referring to the drawingsand more particularlyto Figs. 1 and 2, it will be seen that the duct 20which lis made of unit or standard lengths `(10 feet) joined at theirends, ismprovided with a hinged cover 2l having spring catches 22. Inside the duct, and spaced and insulated therefrom, are bus b ars 24,also made up of unit or r vention, the same being shown in my copendingcase, Serial No. 428,291, Feb. 14, 1930.

' The bus bars 'One of the important features of the invention is themeans for insulating the bus bars, and such means will now be described,in connection with Figs. 2, 9 and 10. The individual bus bars arecovered with long sleeves/21 of rigid insulating material, of suchproportions as to fit on, the

bus bars with a fair degree of friction, whereby they will not shiftaround on the bus bars, ex-

y cept as caused to do so bythe user. The sleeves are so disposed on thebus bars as to leave gaps between their ends, and these gaps are coveredby short sleeves 28'01 rigid insulating material, these sleeves-beinglarge enough to encompass the ends of the small sleeves, with a fairdegree of friction. The inner sleeves 21 are usually kept stationary ontheir'bus bars, and the `outer 'sleeves 28 are slid thereover, to exposeor conceal the bare spots on the bus bars, `between the ends of theinner sleeves. However, the outer sleeves 28 ymay be kept stationary,and the innersleev'es 21 moved to accomplish the same result withoutdeparting from the spirit of the invention.

In Fig. 9 the bus bar 24 is shownas completely insulated by sleeves 21and 2l,-e xcept at vthe bare spot being left for use in a power outletto be located at that point. When for any reason, the location of thepower outlets, and correspondingly of the bare spots, on the bus bars,is to be varied, as for example, to thelayout `of Fig. 10, suitablesleeves 28 are moved to' expose bus bar spots, and certain others may bemoved to conceal already existent bare spots on the bus bars. ComparingFig. 10 with Fig. 9 it will be seen that bare spot X is covered, whilenew ones, at Y,

are created, all this being done without tools, special equipment,taping, etc. diagrammatically show how the location of power outlets maybe varied, multiplied or decreased, merely b y shifting the sleeves 28,and it willbe understood, of course, that the shiftable sleeve idea,brought out in the foregoing, may be carried out more extensively thanshown, if desired.

In Fig. 14 the inner sleeves 21a and the outer sleeves 28a are ofsubstantially the same lengths, and a gap in the insulation may becreated at any point in the bus run.

In Figs. 11 and 12 is shown a'joint between adjacent ends of bus barsections. Each section has anend, slotted as at Il, and an end providedwith plates Il, spaced to receive a slotted end 3l, and provided with asquared hole 32 and a round, hole 33 to receive a screw bolt 34 threaded5 into a'nut 35 to clamp the ends together. The

joint may be insulated by an insulating'sleeve 3B, slidable on the smallsleeves21 to expose the joint.

'I'hese two figures While the sleeves 21 are shown `and described` asmaintained stationary on the bus bars by their own friction producingproportions, it will be understood that other means, such as wooden pegs31 may be used to create friction between the sleeves 21 and the busbars. When such pegs are used, they may be sheared oif by the sleeves28, as the latter are shifted about on the sleeves 21. These pegs alsoserve to space the short sleeves on the longer ones, uniformly. Further,while two sizes of sleeves are shown, it is obvious that but one. sizemay be employed, the sleeves being shifted to vary the location of thebare spots on the bus bars.

' The-power oatlets At unit centers (2ll") on the bottom surface I' ofthe duct, are rectangulaopenings some of which are normally closed byremovably mounted rectangular plates 39 which may be removed to 4I, isplaced against the under side of the duct (Fig. 4) and is boltedthereto, by the shouldered, long bolts 42 and the nuts 42 thereon, thebolts then projecting up in the duct, outside of'the outer pair of busbars. Spacer blocks 44 are then placed between the bus bars and otherspacer blocks 45 are placed between the outer bus bars and the walls ofthe duct, the blocks 4I 44 and 45, having cooperating ribs which serveto align the various blocks with respect to one "another, properly.

Then, if desired, bus bar contacts (Flg; 6) are passed upwardlythroughholes 45a in the block 4I to straddle the bus bars.A Each set ofcontacts includes a pair of leaves 46, pressed to gether by theresilient spring and pin device 41, andlimited in their separatingmovement by a rivet 48.- 'I'he contact leaves 46 are held together, atthe top, by a copper block 49, held in place by a bolt 50, passingthrough the leaves and the block, the'block 49 engaging the undersurface of a top block, described below, to prevent 'the bus bars frommoving vertically in the duct.

Thecontacts of Fig. 6 are designed to cooperate with male contacts 5I onthe outlet plug P. It is possible to provide the outlet plug 'withfemale contactsadapted to receive the bus bar directly (Fig. 7) in whichcase the contactsof Fig. 6 may be dispensed with, or may be replaced byspring leaves 52straddling the bus bars and pressing the female contactsIl of Fig. 7 against the bus bar.

After mounting the receptacle block 4I, the spacer blocks 44 and 45, andthe contacts 48 (if any be used) or the spring leaves 52 (if any beused), atop block 54 is placed on the spacer blocks to complete theinsulation of the outlet, and a top plate B5 is mounted on the top blockto clamp down theblocks. Thetop plate is held down byv the bolts 42 andnuts 56. This completes the formation of the outlet, and it will be seenthat no breaking or cutting of insulation, no taping,

order: nuts 56, top plate 55, top block 54, contact bolts coppervblock49, and contact leaves 45, (or contactsprin'g 52), spacer blocks 44 and45,

` bus bars, the central hole in the outlet plate is provided with akeying cutout 5B (Fig'. 3) which cooperates with a bulge on the outletblock 4| so that the latter can occupy only one position with outletplate.

respect to the plate. The mounting holes for the plate 40 areasymmetrically disposed with respect to the duct opening, and thecontact holes 45a in the outlet'block 4I are asymmetrically disposedwith respect to the .block-itself, in a well known manner, to effect thepolarization of the plug, whose contacts are to pass through the contactholes 45a.,` with respect tothe bus bars. Y v

To reduce manufacturing and assembly and stock costs, 'the spacer blocksare so formed that the inner ones are identical with each other, and theouter pair are also identical with each other. Further, facing surfacesof any two blocks are made duplicates to reduce the cost of dies, etc.used in making the blocks.

to rigidifythe bus bar grouping with respect to with respect to eachother. Usually the outlets are quite close and take 'care of therigidifying sometimes happens that in a long run, there may be nooutlets. In order to rigidifya run, not provided with outlets, agrouping of two blocks 54, one above and one below vthe bus bars, andfour spacing blocks 44 and 45, six in all, iscreated, and mounted aroundthe bus bars, this grouping adequately accomplishing the desired result.Since the parts that are used for a rigidifying group may also be usedas parts of an outlet group, it is unnecessary to stock vspecial parts,whose sole function is to rigidify a bus run.

On the outlet plate 40 at its edges, are two slidthrough which passheaded pins 62, there .being springs 63 to press the locking platesagainst the The outlet plate has holes 64 registeredwith keyhole slots65 in the locking plate, to cooperate with the headed pins 66 of theplug P, and to` Secure the plug in place, under the duct. Means, notshown, are provided on the plug to engage the outletplate and to groundthe plug to the duct, which, in turn, like all conduit, is

' grounded.

It will be noted that the vertical space between outlet block 4`I andtop block 54 is greater than the width of thebus bar shown in Figs. 4and 5.

the one shown may be used in the duct, without difficulty, or redesignof parts, in order to adapt the system. for current-carrying capacities,greater or less than thatl of the 'system shown. This feature is ofimportance in the flexibility of the system.

Now having described the invention and the preferred embodiment thereof,it is to be understood that the said invention is to be limited, not tothe specific details herein set forth, but only by the scope of theclaims which follow:

nuts 43, outlet pme n and block Il, and bons It will be seen thatinsulating blocks 4|, 44', 45, and 54 nbt only form an outlet, but alsoserve the duct and to space and rigidify the bus barsl and spacingrequirements of any bus run, but it able locking putes snrrig. 13)Having slots at 6| If desired, a wider bus bar, or a narrower one, thanf a plurality of removable and replaceable portions closely spaced atuniform distances between the duct supports to permit of access to theinterior of the duct and to the bus bars at any desired ones of closelyand uniformly spaced points between the duct supports, aperturedreceptacles at certain ones of the aforementioned closely spaced pointspermitting access to the bus bars from outside the duct at those pointsthrough the receptacles, the latter being sectional y so that they canbe disassembled and removed from their points of location in the duct,andremounted in other of the aforementioned points in the duct, withoutdestruction of receptacle parts, the receptacles having parts ,whichform barriers between bus bars, and between bus vbars and the walls ofthe duct, to \insulate them electrically and space them physically fromone another and from the duct.

2. In an electrical distribution system, an elongated duct having a wallprovided with spaced certain of said'openings, and receptacles in theduct, at the exposed portions of the bus bars,

the latter being continuous even-as they pass through the receptacles,the latter being assembled on the unsevered bus bars, each ofthereceptacles including an assembly of separate insulating blocksproportioned to be mountable on the-bus bars in the duct, through theopenings, without mutilation of the bus bars, the ducts, or the blocksthemselves, one of which projects throughthe duct-opening and isprovided with spaced holes through which may be passed, from theoutside, means to make electrical contact with the naked bus bars.

'3. In an electrical distribution system, an elongated duct having awall provided with spaced openings, parallel, elongated bus bars in saidduct, and means at the openings to support, space, and insulate the barswith respect' to each other, and with respect to the duct walls, the

means comprising a plurality of insulating blocks 'some of which aredisposed between the bus lgated duct having a wall provided with spacedopenings, parallehelongated bus bars in said duct and having exposedportions aligned with certain of said openings, and receptacles in theduct, at the exposed ,portions of .the bus bars, the latter/beingcontinuous even as they pass through portions of the receptacles, thelatter being assembled on the unsevered bus bars, each of thereceptacles including an assembly of separate insulatingv blocks; one ofwhich projects 'through the duct opening and is provided with spacedholes through which may be passed, from the outside, means to make.electrical.`contact with the naked bus bars, and others of which aredisposed between the bus bars and between the latter and the duct walls,these blocks servlng as insulating barriers for the bars, as well as busrigidifylng and spacing means. v

5. In an electrical dlstributionsystem, an elongated duct havingk awal'lfprovided''withv spaced openings, parallel, elongatedl bus bars' insaid duct, and means at the openings to support, space, and insulate thebars with respect to each other and with respect to the duct walls, themeans comprising a plurality ofinsulating blocks, some of which aredisposed between the bus bars and others of whlch'are disposed bev'tweenthe bus bars and the duct walls, the blocks being assembled on the busbars without severing the latter, these being lcontinuous, from end toend, even as they pass Aby, the openings, certain of the blocks beingdesigned'so as to be useful, not only as spacing and insulatingblocks,but as parts of an outlet receptacle, if one is to be substituted forthe spacing means'.

6.' In an electrical distribution-system, a sheet metal duct ofsubstantially rectangular cross section having an opening in one of itssurfaces, a plurality ofy parallel bus bars longitudinally disposed inthe duct and passing said opening, and means forming an voutlet orreceptacle at the opening, said means including a plurality of separateinsulating blocks disposed between and around the bus bars at theopening and insulating of the bus bars from one another and from `thewalls of the duct, the blocks being separate and independent and of asize whereby they will be capable of being assembled on the bus barsthrough the opening to form a receptacle, or being disassembled from thebus bars and removed through the opening, Without disturbing the bars,the blocks filling substantially the entire lvolume of the duct at theopening andbeing held-therein by the walls of the duct and theindependent and of a size whereby they. will be capable of beingassembled ,on the bus bars through the opening to form a receptacle, or

being disassembled from the bus bars and re.

moved through the opening, without disturbing the bars, the blocksfilling substantially the entire volume of the duct at the opening andbeing `held therein by the walls of the duct and the -bus bars, theassembly of blocks being provided with a portion projecting into andillling the duct opening and having plug contact receiving apertures.

8. Inl an electrical distribution system, a sheet metal duct ofsubstantiallyrrectangular cross secr tion having an opening in one ofits surfaces, a plurality of parallel bus bars longitudinally disposedin the duct and passing ysaid opening, and means forming `an outlet orreceptacle at the opening, said means including a plurality of separateinsulating blocks disposed between and around the bus bars at theopening and insulate thel`x bars, the blocks illlingv substantially,``the 'en-( tire volume of the duct at the opening'` and beingheld"therein bye-the walls'of, the duct'ad the bus bars, theassembly ofblocks being'lprovidedl;

withl a portion projecting, intol and llingthe duct lopening and havingplug (,:ont'ac receiving apertures provided witlrpontact receiving.sockets.

9. In an electric distributing system, an openended tube vofsubstantially uniform cross section throughout its length provided inone side with openings, means within and adjustable longitudinally ofthe tube to any point thereof for supporting bus bars, including a blockoi ,insulating Amaterial having a, base extending longitudinallyof thetub`e and provided at substantially the longitudinaly median linethereof with a longitudinally extending rib, insulating material withinthe tube upon opposite sides of the base, bushing means projecting fromthe block through certain one of the tube openings, bus bars extendinglongitudinally of the tube, two of said bars being between the rib andinsulatingY openings, bus bars extending longitudinally of said tube,means within and adjustable longitudinally of the tube forsupportingsaid bus bars including a block of insulating material having alongitudinally extending rib serving as a seat for one of said bus bars,opposite sides of the rib receiving the other bus bars, insulating meansprojecting from the block through a certain' one of the openings in thetube, and electrical conductors connected to the bus bars and extendingoutwardly atleast partially through the block and insulating meansaforesaid.

11. In an electric distributing system, a closed trough of'substantially uniform fcross section throughout its length provided inone side with openings, means within and adjustable 1ongitu. dinally ofthe trough to any point thereof for supporting bus bars, includingablock of insul lating material having a base extending longitudinally ofthe trough, insulating material within the trough upon opposite sides ofthe base, bushing means projecting from the block ,through a certain oneof the openings, bus bars extending longitudinally of the trough, twoof, said bars being between portions ofthe base and insulating material,and' electrical conductors secured to said bus bars and. extendingoutwardly at least partially through the block and bushing meansaforesaid. v

12. In an electric distributing system, an openended tubeofsubstantially uniform cross section throughout its length provided Vinone side with openings, means within and adjustable longitudinally ofthe tube to any point thereof for supporting bus bars, including blocksof insulating material having bases extending longitudinally of Ithetube and provided at substantially their longitudinal median lines-withlongi tudinally extending ribs, insulating material within the tube uponopposite sides o'f the bases,

. ing material having bases extending longitudibushing means projectingfrom theV blocks through certain of the openings, bus bars extendinglongitudinally of the tube, two of said bars being between the ribsand'insulating material, and the third extendingr lonigtudinally of theribs, and electrical conductors secured to said bus barsand extendingoutwardly at least partially through the blocks and bushing meansaforesaid.

13. In an electric distributing system, an openended tube ofsubstantially uniform cross section through its length provided in oneside with openings, means within and adjustable longitudinally of thetube to any point thereof for supporting bus bars, including blocks ofinsulating material having bases extending longitudinally of the tubeand provided at substantially their longitudinal median lines withlongitudinally extending ribs, said ribs and bases having openings inalignment with certain oi' the openings, busbars extending longitudinally of the tube, one on each side of the ribs, and one extendinglongitudinally of the ribs, and electrical conductors secured to saidbus bars and extending outwardly at least partially through the openingsin, ihe ribs and bases and through certain oi' the openings in the tube.

14. In an electric distribution system, an open-ended tube oi1substantially uniform cross section throughout its length provided inone side with openings, bus bars extending longitudinally of said tube,means within and adjustable longitudinally of the tube for supportingsaid bus bars including blocks of insulating material havinglongitudinally extending ribs serving as seats for `one of said bus barsand having longitudinallyl extending recesses upon opposite sides of theribs,V the other bus bars being on opposite sides of the ribs,insulating means projecting from the blocks through certain of theopenings in the tube, and electrical conductors connected to the busbars and extending at least partially through the blocks and insulatingmeans aforesaid.

15. In an electric distributing system, a closed trough o1'substantially uniform cross section throughout its lengthprovided in oneside with openings, means within and adjustable longitudinally of thetrough to any point thereof for supporting bus bars, including blocks ofinsulatnally of the trough, insulating material within the trough uponopposite sides of the bases, bushcertain of the openings, bus barsextending longitudinally of the trough, two of said barsbeing betweenportions oi' the bases and insulating material, and electricalconductors secured to said bus bars and extending outwardly at leastpartially through the blocks and bushing means aforesaid.v l

16. In an electric distributing system, a closed throughout its lengthprovided in one side with openings, means within and adjustablelongitudinally of the troughv to any point thereof for supporting busbars, including blocks oftinsulating material having bases extendinglongitudinally of the trough, said bases having openings in alignmentwith certain of the openings, bus bars extending longitudinally oi' thetrough and mounted on the bases, and electrical conductors ing meansprojecting from the blocks throughl trough of substantially uniformcross section secured to said bus bars and extending outwardly at leastpartially through the openings in theY bases and through certain of theopeningsA in the trough. Y

17. In an electrical distribution system, an elongated duct having awall provided with spaced openings, parallel, elongated bus bars in saidduct and having exposed portions aligned with certain of said openings,and receptacles in the duct, at the exposed portions of the bus bars,

the latter being continuous, even as they pass through portions of thereceptacles, the latter being assembled around'the unsevered bus bars,the

receptacles including portions projecting through the duct openings andprovided with spaced holes through which may be passed, from theoutside, means to make electrical contact with the bus bars, andportions disposed between the bus bars and between the latter and theduct walls, these receptacles serving as insulating barriers for'thebars, as well as bus rigidifying and spacing means.

18. In an electrical distribution system, an` elongated duct having aWall provided with spaced openings, parallel, elongated bus bars in saidduct and having exposed portions aligned with certain of said openings,and receptacles in the duct at the exposed portions of the bus bars,including portions projecting through the duct opening and provided withspaced holes through which may be passed, from the outside, means tomake electrical contact with the busbars, and contactsstraddling and incontact with the naked bus bars and disposed in alignment with saidreceptacle holes so as to be accessible through the latter, fromy theoutside.l

19. In an electrical distribution system, an

I elongated duct having a wall provided with spaced openings, parallel,elongated bus bars in said duct,y and means at the openings to support,space, an

insulate the bars with respect to each other and with respect to theduct Walls, Ithe means comprising a plurality of insulating portions,some of which'are disposed between the bus bars and between the bus barsand the duct walls, the portions being assembled with respect to the busbars without severing the latter, these being continu' ous, from end toend', even as they pass by the openings,v certain of the portions beingdesigned So as to be useful, not only as spacing and insulating means,but as parts of an outlet receptacle.

20. In an electrical distribution system,ja sheet metal `duct ofsubstantially rectangular cross section having openings in one of itssurfaces, a plurality of parallel bus bars longitudinally disposed inthe duct and passing said openings, and means v and removed Withoutdisturbing the bars, 'the blocks covering substantially the entire areaof the duct wall at the openings and being held therein by the walls ofthe duct and the bus bars. y

21. In an electrical distribution system, a sheet metal duct ofsubstantially rectangular cross sec' tion having openings in one of itssurfaces, a plurality of parallel bus bars longitudinally disposed inthe duct and passing said openings, and means forming outlets or`receptacles at the openings,

said means including a plurality of separate insulating blocks disposedbetween and around the bus oars at the openings and insulating the busbars from one another and from the walls of the duct, the blocks beingseparate and independent and of a size whereby they will be capable oi'being assembled on the bus bars to form receptacles,

or being disassembled from the bus bars and removed without disturbingthe bars, the blocks covering substantially the entire area of the ductwall at the openings and being held therein by the walls of the duct andthe bus bars, the blocks being provided with portions projecting intoand filling the duct openings and having conductor receiving apertures.

22. An electrical distribution system comprising a long run of ductlexternally supported on spaced supports and having a cover which may bemoved to expose the interior of the duct wherever.

desired and a plurality of long runs of relatively insulated bus bars insaid duct, the duct having a plurality of openings closely spaced atuni-I form distances between the duct supports to permit of access tothe interior of the duct and to the-bus bars at any desired ones ofclosely and uniformly spaced points between the duct supports, theseopenings having shiftable shutters. apertured plug prong receivinginsulator housing structures within the duct at certain ones of theaforementioned openings, which openings permit of plug prong insertionto the bus bars from outside the duct at those points, the housingsreceiving the prongs and isolating them from one another when the prongsare inserted and being so constructed and arranged as to confine arcsformed on separation of prongs ,from bus bars to the immediate vicinityof the prongs and to the interiors of the housings, the housings'beingreadily separable from or mountable on the bus bars and in the ductwithout requiring the disassembly of the duct or the bus bars, thesebeing continuous, from end to end, even as they pass housings, and beingso formed and dimensioned with respect to the duct openings that theycan be removed from the duct or inserted into the duct through theopenings. Y

23. In an electrical distribution system, a sheet metal duct ofsubstantially rectangular cross section having an opening in one of itssurfaces, a plurality of parallel bus bars longitudinally. disposed inthe duct and passing said opening, and means forming an insulatingoutlet or receptacle structure at the opening, said means beingdislposed between and around the bus bars at the opening and insulatingthe bus bars from one another and from the Walls of the duct, thestructure being so formed and' so dimensionedtthat it is capable ofbeing assembled on the bus bars through the opening to form a receptaclestructure, or being disassembled from the bus bars and removed throughthe opening, without disturbingv said hole whereby it may be engaged bya busba'l engaging prong of a branch circuit plug inserted into the ductthrough said hole, an insulation structure having a part so proportionedto the Vhole that it may be projectedtherethrough, and

having a part so proportioned to the hole that it I may not be projectedtherethrough, the shoulder thus provided engaging-said duct wall tolimit movement of the structure in the ductV hole, -the V structuresealing the hole and' adapted to be assembled with Vrespect to the duct-around the bus'bar and removed from the duct and from around the busbar without requiring severance or mutilation of the bus bar, thestructure having a part provided with a surface outside the duct, thestructure having a prong way opening to the surface and leading into theduct toa bus bar,

the structure isolating the prong way.

25. In an electrical distribution system, a duct having a wallV normallystationary with respect to the duct as a whole and provided with anopening, a bus bar having a portion exposed at said hole whereby it maybe engaged by a bus bar engaging prong of a branch circuit plug insertedinto the duct through said hole, an insulation structure having a partso proportioned to the hole that it may be projected therethrough, and

v having a part so proportioned to the hole that it may not be projectedtherethrough, the shoulder thus provided engaging said duct wall tolimit movement of the structure in the duct hole, the structure sealingthe hole and adapted to be assembled with respect to the duct around'thebus bar and` removed from the duct and from` around the bus bar withoutrequiring rseverance or 'mutilation of the bus bar, the structure havinga partI provided with a surface outside the p duct, the structure havinga prong way opening to the surface and leading into the duct to a. busbar in said prong way, the structure isolating the prong way and thelexposed portion of the bus bar therein.

a' part so proportioned to the-hole that it may not be projectedtherethrough, the shoulder thus provided engaging said duct wall tolimit movement of the structure in 'the duct hole, the structure sealingthe hole and adapted to be assembled with respect to the duct around thebus bars and removed from the duct and from around the bus bars withoutrequiring severance or mutilation of the bus bars, the structure havinga part provided with a surface outside the duct, the structure havingprong ways opening tothe surface and leading into theduct to thebus-bars, the structure isolating the prong ways.-

27. In an electrical distribution system, .a duct having a wall normallystationary with respect to the duct as a whole and provided with anopening, bus barsv having portions exposed at said hole whereby they maybe engaged by bus bar engaging prongs of a branch circuit plug insertedinto the duct through said hole, an insulation structure `having a partso proportioned to the hole that it may be projected therethrough andhaving a part so proportioned to the hole that it may not be projectedtherethrough, the shoulder thus provided engaging said ,duct wall tolimit movement ofthe structure in the duct hole, the structure sealingthe hole and adapted to be assembled with respect to the duct around thebus bars and removed from the duct and from around the bus bars withoutrequiring severance or mutilation of thebus bLars, the structure havinga' part provided with la surface outside the-duct, the.structure havinglh-ong ways open.

ing to the surfacev and leading into the duct to the bus bars in saidprong ways, the structure Y isolating the prong ways and the bus barstherein.

28. In an electrical distribution system, a duct having a wall normallystationary with respect to the duct as a Whole and provided withlongitudinally spaced openings, a bus bar having por- Q tions exposed atsaid holes whereby it may be engaged by bus bar engaging prongs ofbranch circuit plugs inserted into the duct through said holes,insulation structures at certain holes, each having a part soproportioned to each hole that it may be projected therethrough andhaving a part so proportioned to the hole that it may not be projectedtherethrough, the shoulder thus provided engaging said duct wall tolimit movement of the structure in the duct hole, the structures sealingthe holes and adapted tobe assembled with respect to the duct around the'bar and re- `moved from the duct and from around the bus bar withoutrequiring severance or mutilation of the bus bar, each structure havinga part provided with a surface outside the duct, each 'structure havinga prong Way opening to the surface -and leading vinto the duct to thebus bar, the

structure isolating the prong way, the structures being transferable toand from holes without requiring mutilation of the bus bar, ,andshutters for holes not equipped with such structures.

29. In' an electrical distribution system, a duct having a Wall nprmallystationary with respect to the duct as a whole and provided withlongitudinally spaced openings, a bus bar having portions exposed atsaid holes whereby it may be engaged by bus bar engaging prongs ofbranch circuit plugs inserted into the duct through said holes,insulation structures at certain holes, each having a part soproportioned to each hole that it may be projected therethrough andhaving a part soproportioned to the holethat it may .not be projectedtherethrough, the shoulder thus provided engaging said duct Wall tolimit movement of the structure in the duct'hole, the structures sealingthe holes and adapted to be assembled with respect to the duct aroundthe bar and removed from the duct and from aroundI the bus bar Withoutrequiring severance or mutilation of the bus bar, each structure havinga part provided with a surface outside the duct, each structure having aprong way opening to the surface and leading into the duct to the busbar in said prong way, the structure isolating the prong Way and theexposed portion of the bus bar therein, the structures beingtransferable to yand from holes without requiring mutilation of the busbar, and shutters fr holes not equipped with such structures.

30. In an electrical distribution system, a duct having a wall normallystationary with respect to the duct as a Whole and provided withlongitudinallyspaced openings, bus bars having portions exposed at saidholes whereby they may be engaged by bus bar engaging prongs of branchcircuit plugs inserted into the duct through said holes, insulationstructures at certain holes, each having a part so proportioned to eachhole thatr it may be projected therethrough and having 'a partsoproportioned to the hole that it may not be projected therethroughtheshoulderthus provided engaging said duct Wall to limit movement of thestructure in the duct hole, the structures sealing the holes and adaptedto bc assembled with respect to the duct around the bus bars and removedfrom the duct and from around the bus bars Without requiring severanceor mutilation of the bus bars, each structure having a part providedwith a surface outside the duct, each structure having prongways openingto the surface and leading into the duct tothe bus bars, the structuresisolating the prong Ways, the structures being transferable to and fromholes without requiring mutilation bf the bus bars, and

shutters for holes not equipped with such structures.

31. In an electrical distribution system, a duct having a wall normallystationary Withrespect to the duct as a whole and .provided withlongitudinally spaced openings, bus bars having portions exposed at saidholes whereby they may bel engaged by bus bar engaging prongs of branchcircuit plugs inserted into the duct through said holes, insulationstructures at certain holes, each having a part so'proportioned to eachhole that it may be projected therethrough and having a part soproportioned to the hole that it may not be projected therethrough, theshoulder thus provided engaging said duct wall to limit movement of thestructure in the duct hole, thelstructures sealing the holes andadaptedto be assembled with respect to the duct around the bus bars andremoved from the duct and from around the bus bars without requiringseverance or mutilation of the bus bars, each structure having a. partpro- HARRISON AJ. L. FRANK. I

